Investigating Immunomodulatory roles of CX3CR1 Related with Differentiation and Functional Polarization of Kupffer Cells

Abstract

Background: Even though there were many studies to identify the origin of Kupffer cells (KCs) KCs, resident macrophage in the liver, it has not been elucidated clearly. CX3CR1 which is a kind of chemokine receptor is expressed on various monocyte-macrophage lineage cells and is known to relate with liver diseases. In the present study, we investigated the role of CX3CR1 for development of KC.

Methods: For differentiation of macrophages from monocytes, sorted monocytes from mice liver and human PBMCs were co-cultured with liver sinusoidal endothelial cells (LSECs) and human umbilical venous endothelial cells (HUVECs). The populations of monocyte and KCs were analyzed in CX3CR1GFP/GFP mice which is deficient of CX3CR1and CX3CR1+/GFP mice as control after treatment of clodronate liposome for depletion of KCs. Alcoholic liver injury was achieved by feeding with 5% liquid ethanol diet for 8 weeks to CX3CR1+/GFP and CX3CR1GFP/GFP mice.

Results: Isolated monocytes from liver and spleen were changed their morphology and cell surface marker with support of LSECs. Moreover, human circulating monocytes could be also differentiated to macrophage-like cells. During recovery period after clodronate treatment, the population of GFP+ macrophage were significantly decreased in CX3CR1 deficient mice compared to control mice. Interestingly, pro-inflammatory molecules such as IL-6, MCP-1 and TNF-alpha were highly expressed in F4/80 high cells from CX3CR1+/GFP mice, while F4/80 high cells which were originated from CX3CR1GFP/GFP mice exhibited abundant expression of anti-inflammatory molecule like arginase-1, IL-10 and TGF-beta. Moreover, CX3CR1 deficiency reduced serum level of AST/ALT and reduced fat accumulation compared to control in alcohol-induced liver injury (Figure).

Conclusions: CX3CR1 is important factor in development and anti-inflammatory functional differentiation of KCs. Therefore, CX3CR1 could be not only novel therapeutic target for various kind of liver disease but also key molecule for studying of macrophage origin.